The present invention relates to monolithic electronic integrated circuits, and, more particularly, to a monolithic electronic integrated circuit for a programmable data acquisition system employed for collecting electrical power signals and coupled to an external microprocessor for correcting magnitude and phase of quantized measurement signals supplied by the data acquisition system.
Several conflicting objectives are present in the field of high performance data acquisition for electrical power measurement, metering, and management. A first objective is high data resolution. The availability of high resolution analog-to-digital conversion methods, such as with sigma-delta modulators, combined with the power of state of the art digital signal processors provides the capability to achieve significant levels of accuracy. Thus, any suitable signal processing may be performed on precise data using conventional signal processing architectures. However, a second objective is increased signal processing bandwidth. An inherent tension exists between these two objectives in that increasing bandwidth typically occurs at the expense of data resolution. Yet, a third objective is compactly integrated or electronic circuitry that requires less power to operate. A need thus exists for a data acquisition system having the capability to balance high data resolution demands against large bandwidth demands, as desired for power measurement, metering, and management systems, while having the size and power requirements of a conventional electronic or integrated circuit component. As suggested above, analog-to-digital converters of delta-sigma type are particularly economical of digital hardware. The use of such converters introduce into the system sinc.sup.k decimation filters, in which the kernal is a sampled-data representation of a suitable time-domain response, to achieve sufficient selectivity against harmonic components of the sinusoid being filtered. For example, for k=1 the time domain response corresponds to a rectangular time response, while for k=2, the time domain response corresponds to a triangular time response. In each case, the magnitude response of such sinc.sup.k filters generally introduces considerable attenuation over the high-end of a desired passband range. Thus it is desirable to provide a data acquisition system capable of providing both a substantially uniform magnitude and a substantially linear phase response over the desired bandpass range. Further, since the data acquisition system may receive analog input signals from a plurality of sensors, such as voltage and current sensors, each having a respective phase angle characteristic, it is also desirable to provide a data acquisition system capable of providing phase angle correction while operating in a manner consistent with providing a substantially linear phase response over the bandpass range of interest.
It is also desirable to provide a data acquisition system capable of performing preventative diagnostics in the field without having to wait until a "hard failure" occurs and all operational capability is lost. Thus a need exists for providing a data acquisition system which provides substantial operational capability even while undergoing testing. It is further desirable to provide a data acquisition system that includes a feedback circuit for interfacing with sensors, such as zero-flux current sensors, that may require a feedback signal to avoid core saturation in the presence of large current loads.